This core facility will test immune sera and purified immunoglobulins for the ability to block HIV replication in established T-cell lines and fresh human peripheral blood mononuclear cells (PBMC). This will involve maintenance in tissue culture of MOLT-4, CEM PBMCs and other cells permissive for HIV-1 replication, production, tittering, and storage of viral stocks, establishment of HIV-1 chronically infected T cells for syncytium formation, testing of sera and immunoglobulin preparations for neutralization of HIV-1 isolates in syncytium inhibition and micro- reverse transcriptase assays, as well as analysis, storage and transmission of data to Principal Investigators of the NCVDG. Over 23 different immunogen/adjuvant formulations will be tested in mice, rabbits, rhesus macaques and samples per year which will need to be tested in HIV neutralization assays.